A Scorer which wraps another scorer and caches the score of the
current document. Successive calls to score() will return the same
result and will not invoke the wrapped Scorer's score() method, unless the
current document has changed.
This class might be useful due to the changes done to the Collector
interface, in which the score is not computed for a document by default, only
if the collector requests it. Some collectors may need to use the score in
several places, however all they have in hand is a Scorer object, and
might end up computing the score of a document more than once.

Advances to the next document in the set and returns the doc it is
currently on, or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the
set.NOTE: after the iterator has exhausted you should not call this
method, as it may result in unpredicted behavior.

nextDoc

Advances to the next document in the set and returns the doc it is
currently on, or DocIdSetIterator.NO_MORE_DOCS if there are no more docs in the
set.NOTE: after the iterator has exhausted you should not call this
method, as it may result in unpredicted behavior.

advance

Advances to the first beyond the current whose document number is greater
than or equal to target, and returns the document number itself.
Exhausts the iterator and returns DocIdSetIterator.NO_MORE_DOCS if target
is greater than the highest document number in the set.

The behavior of this method is undefined when called with
target ≤ current, or after the iterator has exhausted.
Both cases may result in unpredicted behavior.

NOTE: this method may be called with DocIdSetIterator.NO_MORE_DOCS for
efficiency by some Scorers. If your implementation cannot efficiently
determine that it should exhaust, it is recommended that you check for that
value in each call to this method.